A minister is a politician who heads a ministry, making and implementing decisions on policies in conjunction with the other ministers. In some jurisdictions the head of government is also a minister and is designated the ‘prime minister’, ‘premier’, ‘chief minister’, ‘chancellor’ or other title.

In Commonwealth realm jurisdictions which use the Westminster system of government, ministers are usually required to be members of one of the houses of Parliament or legislature, and are usually from the political party that controls a majority in the lower house of the legislature. In other jurisdictions—such as Belgium, Mexico, Netherlands, Philippines, Slovenia, and Nigeria—the holder of a cabinet-level post or other government official is not permitted to be a member of the legislature. Depending on the administrative arrangements in each jurisdiction, ministers are usually heads of a government department and members of the government's ministry, cabinet and perhaps of a committee of cabinet. Some ministers may be more senior than others, and some may hold the title ’assistant minister’ or ‘deputy minister’. Some jurisdictions, with a large number of ministers, may designate ministers to be either in the inner or outer ministry or cabinet.

In some jurisdictions—such as Hong Kong, Mexico, the Philippines, the United Kingdom, and the United States—holders of an equivalent cabinet-level post are called secretaries (e.g., the Home Secretary in the United Kingdom, Secretary of State in the United States). Some holders of a cabinet-level post may have another title, such as ’Attorney-General’ or ’Postmaster-General’.